Adhesive tapes containing a woven cloth backing are widely used, such as in conventional duct tapes sold to consumers and professionals. One of the advantages of using woven cloth as a tape backing is that it provides a combination of high tensile strength and low elongation to break in both the length or machine direction (“MD”) of the tape and in the width or transverse direction (“TD”) of the tape. For many applications, this high strength and low elongation can be very important. Another advantage provided by tape backings is the relative ease of straight-line tearing along each of these two principle directions. Woven cloth backings also have drape and conformability characteristics that are desirable in many tape applications, and provide an appearance that is considered desirable in the marketplace for many kinds of adhesive tapes that have traditionally been made with woven cloth backings.
Woven cloth also has several disadvantages as an adhesive tape backing. In many applications, the woven structure must be saturated by the adhesive used in the tape, leading to the use of larger amounts of adhesive than for a film-backed tape. In some applications, a smooth or non-fibrillar top surface of the tape is desired, so the cloth backing must be overlaminated or coated. Also, hand-tearing cloth-backed tapes frequently results in loose fibers protruding from one or both torn edges. Finally, cloth backings are generally more expensive than polymeric film backings.
A polymeric film suitable for use as a backing material for tapes, as well as for use in other applications that require high tensile strength and straight-line tearing, is described in WO 200211978A, entitled “Cloth-like Polymeric Films.” The film in WO '978 has a plurality of elongate oval perforations configured and arranged in a manner such that the film exhibits many of the properties of cloth materials. U.S. Pat. No. 4,609,107 by Martin et al. describes a line of specially shaped, closely spaced apart perforations that provide a controlled tear line for an easy-open plastic bag used to package snack foods. Tear-inducing cuts and apertures in the shape of straight slits, circular holes, “L”-shaped, “V”-shaped or “U”-shaped cuts along the length (MD) of a packaging tape are described in WO 96/24549. Corrugated thermoplastic articles comprising at least two uniaxially oriented sheets of crystalline polymer and methods for preparing such sheets are described in U.S. Pat. No. 3,649,431 by Parker. To form the corrugated construction of Parker, the multiple sheets are fusion bonded at the peripheries of closely spaced perforations. For particular applications, a desire still exists for an alternative polymer film tape backing that combines, at low cost, the strength, elongation, tear, and conformability properties of woven fabric and provides a less jagged, tear line along a desired tear path, while maintaining tensile strength in a direction perpendicular to the tear line.